Berlin 2015 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 99: Superconductivity: (General) Theory 2
TT 99.7: Talk
Thursday, March 19, 2015, 16:30–16:45, H 2053
Collective modes in superconductors without inversion symmetry — •Nikolaj Bittner1, Dietrich Einzel2, Ludwig Klam1, and Dirk Manske1 — 1Max–Planck–Institut für Festkörperforschung, D–70569 Stuttgart, Germany — 2Walther–Meißner–Institut für Tieftemperaturforschung, D–85748 Garching, Germany
The collective modes characteristic of conventional and unconventional superconductors include the Anderson–Bogoliubov (or gauge) mode ωG as well as the condensate plasma mode ωP, to which the gauge mode gets shifted as a consequence of the Anderson–Higgs mechanism (AHM). A unique property of non–centrosymmetric superconductors (ncs) is the coexistence of spin–singlet (Δs) and triplet (Δtr) energy gaps. In the limit of strong spin–orbit coupling there arises a two–band (two–gap) structure, which automatically implies the existence of a new massive collective mode ωL, discovered by A. J. Leggett in 1966 for ordinary two–band superconductors, the so–called Leggett mode. In this contribution we focus on the analysis of the electromagnetic response of the superconducting condensate and specify for the first time the collective modes ωG, ωP and ωL in ncs systems of cubic and tetragonal symmetry. Particular emphasis is on the analysis of Leggett’s collective mode in ncs systems for which we can show that (i) it is, besides the gauge mode, necessary to guarantee charge conservation, (ii) the AHM only slightly modifies its dispersion and leaves its mass unaffected, (iii) it survives in the limit of vanishing triplet admixture t = Δtr /Δs to the singlet energy gap and (iv) its form is symmetry–dependent (cubic, tetragonal) for finite triplet admixture t.